From 88192ffb7072e8b86c392ef41e4e8958e98f1f46 Mon Sep 17 00:00:00 2001
From: Joe Groff <jgroff@apple.com>
Date: Tue, 20 Feb 2024 16:40:36 -0800
Subject: [PATCH] SILGen: Unwrap `@moveOnly` wrapped values before yielding
 them.

---
 lib/SILGen/SILGenApply.cpp                    | 14 +++++++++++--
 test/SILGen/yield_borrowing.swift             | 20 +++++++++++++++++++
 .../moveonly_borrowing_switch.swift           | 10 ----------
 3 files changed, 32 insertions(+), 12 deletions(-)
 create mode 100644 test/SILGen/yield_borrowing.swift

diff --git a/lib/SILGen/SILGenApply.cpp b/lib/SILGen/SILGenApply.cpp
index 6c099141765..22e31224ea1 100644
--- a/lib/SILGen/SILGenApply.cpp
+++ b/lib/SILGen/SILGenApply.cpp
@@ -6011,8 +6011,18 @@ void SILGenFunction::emitRawYield(SILLocation loc,
                                   JumpDest unwindDest,
                                   bool isUniqueYield) {
   SmallVector<SILValue, 4> yieldValues;
-  for (auto arg : yieldArgs)
-    yieldValues.push_back(arg.getValue());
+  for (auto arg : yieldArgs) {
+    auto value = arg.getValue();
+    if (value->getType().isMoveOnlyWrapped()) {
+      if (value->getType().isAddress()) {
+        value = B.createMoveOnlyWrapperToCopyableAddr(loc, value);
+      } else {
+        value = B.createGuaranteedMoveOnlyWrapperToCopyableValue(loc, value);
+      }
+    }
+    
+    yieldValues.push_back(value);
+  }
 
   // The normal continuation block.
   auto resumeBB = createBasicBlock();
diff --git a/test/SILGen/yield_borrowing.swift b/test/SILGen/yield_borrowing.swift
new file mode 100644
index 00000000000..7d845d86c27
--- /dev/null
+++ b/test/SILGen/yield_borrowing.swift
@@ -0,0 +1,20 @@
+// RUN: %target-swift-emit-silgen -verify %s
+struct Foo {
+    var x: String
+
+    var y: Foo {
+        borrowing _read {
+            yield self
+        }
+    }
+}
+
+struct BigFoo {
+    var x: Any
+
+    var y: BigFoo {
+        borrowing _read {
+            yield self
+        }
+    }
+}
diff --git a/test/SILOptimizer/moveonly_borrowing_switch.swift b/test/SILOptimizer/moveonly_borrowing_switch.swift
index b7a25d4144d..a0710e61f54 100644
--- a/test/SILOptimizer/moveonly_borrowing_switch.swift
+++ b/test/SILOptimizer/moveonly_borrowing_switch.swift
@@ -299,10 +299,6 @@ extension List {
         }
     }
 
-/*
-    TODO: type mismatch because of `@moveOnly` wrapper. yield needs to peel it
-    off
-
     var head: Element {
         _read {
             switch self {
@@ -313,7 +309,6 @@ extension List {
             }
         }
     }
-*/
 }
 
 extension ChonkyList {
@@ -335,10 +330,6 @@ extension ChonkyList {
         }
     }
 
-/*
-    TODO: type mismatch because of `@moveOnly` wrapper. yield needs to peel it
-    off
-
     var head: Element {
         _read {
             switch self {
@@ -349,6 +340,5 @@ extension ChonkyList {
             }
         }
     }
-*/
 }